US9680076B2 - Light-emitting device, illumination device and backlight for display device - Google Patents

Light-emitting device, illumination device and backlight for display device Download PDF

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US9680076B2
US9680076B2 US14/410,469 US201314410469A US9680076B2 US 9680076 B2 US9680076 B2 US 9680076B2 US 201314410469 A US201314410469 A US 201314410469A US 9680076 B2 US9680076 B2 US 9680076B2
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light
resin
face
faces
emitting device
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US20150340576A1 (en
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Shin Itoh
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Sharp Corp
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Sharp Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/58—Optical field-shaping elements
    • H01L33/60—Reflective elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0013—Means for improving the coupling-in of light from the light source into the light guide
    • G02B6/0023—Means for improving the coupling-in of light from the light source into the light guide provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
    • G02B6/0031—Reflecting element, sheet or layer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
    • H01L25/03—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes
    • H01L25/04—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
    • H01L25/075—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00
    • H01L25/0753—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00 the devices being arranged next to each other
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/50—Wavelength conversion elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/62—Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0066—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form characterised by the light source being coupled to the light guide
    • G02B6/0073—Light emitting diode [LED]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/481—Disposition
    • H01L2224/48135—Connecting between different semiconductor or solid-state bodies, i.e. chip-to-chip
    • H01L2224/48137—Connecting between different semiconductor or solid-state bodies, i.e. chip-to-chip the bodies being arranged next to each other, e.g. on a common substrate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/00014—Technical content checked by a classifier the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Definitions

  • the present invention relates to a light-emitting device having a light-emitting element such as an LED (light-emitting diode), and to an illumination device and a backlight for a display device, each provided with such a light-emitting device.
  • a light-emitting device having a light-emitting element such as an LED (light-emitting diode), and to an illumination device and a backlight for a display device, each provided with such a light-emitting device.
  • a conventional light-emitting device provided with an LED is disclosed, for example, in Patent Document 1 identified below.
  • an LED is embedded in a molding (reflector) which has formed thereon a first reflective face which is increasingly wide open from the bottom face of the molding upward and a second reflective face which is contiguous with the first reflective face and is increasingly wide open further upward, and the LED is sealed in resin from around.
  • the inclination angle of the second reflective face is so set as to be larger than 0° but smaller than the critical angle at the interface between the resin and the layer of air. With the inclination angle of the second reflective face so set, more of the light that is totally reflected on the interface, is then totally reflected on the second reflective face, and is then incident on the interface again can be extracted, achieving improved light extraction efficiency.
  • the first reflective face (inner wall) of the molding is located close beside the LED, and the light emergent from the LED is incident on the inner wall directly (across a short distance). This may discolor the inner wall and shorten the lifetime of the package.
  • the white resin turns increasingly yellow, which significantly lowers the light output of the package and significantly shortens the lifetime of the package.
  • a metal lead frame is bent to form a recess, which is surrounded by a reflector, and an LED is arranged on the bottom face of the recess and is sealed in transparent resin.
  • the light emergent from the LED is reflected on the side face of the recess, and this reduces the light that is directly incident on the inner wall of the reflector. It is thus possible to alleviate discoloration of the inner wall and to prolong the lifetime of the package.
  • Patent Document 2 also discloses a structure in which an LED is arranged on one of a plurality of metal lead frames arranged apart from one another and the electrodes of different polarities of the LED are electrically connected to different ones of the metal lead frames via bonding wires respectively, wherein the metal lead frames each have a fin portion formed integrally therewith.
  • the fin portion is provided at opposite sides of a bottom portion of each metal lead frame, with an inclination relative to the bottom portion, so as to form reflective faces. Also with this structure where the light from the LED arranged in the bottom portion of the metal lead frame is reflected on the fin portion, it is possible to reduce the amount of light that is directly incident on the inner wall of the reflector and to alleviate discoloration of the inner wall.
  • Patent Document 1 JP-A-2010-62427 (claim 1, paragraphs [0018] and [0019], FIGS. 1 and 2, etc.)
  • Patent Document 2 JP-A-2008-53726 (paragraphs [0009], [0026], and [0037], FIGS. 5 and 8, etc.)
  • Patent Document 2 discloses nothing about the range of the inclination angle of the reflective faces provided at the side of the LED. Thus, depending on the inclination angle of the reflective faces, it can occur that, when the light emergent sideways from the LED is incident, via those reflective faces, on the interface between the resin in which the LED is sealed and the layer of air, a higher proportion of the light is reflected there, making it impossible to efficiently extract the light incident on the interface.
  • the range of the inclination angle of the second reflective face is so wide that it cannot necessarily be said that a satisfactorily improvement in light extraction efficiency is achieved there.
  • the inclination angle of the second reflective face approaches 0°, the closer to 90° the angle of incidence of the light incident on the interface between the resin and the layer of air, the more likely the light that is totally reflected on the interface, is then reflected on the second reflective face, and is then incident on the interface again is totally reflected there, leading to lower light extraction efficiency.
  • an object of the present invention is to provide a light-emitting device that can satisfactorily improve the efficiency of extraction of the light emitted from a light-emitting element to outside while suppressing discoloration of an inner wall of a package, and to provide an illumination device and a backlight for a display device, each provided with such a light-emitting device.
  • a light-emitting device is provided with: a light-emitting element arranged on one of a plurality of metal lead frames arranged apart from one another; and a reflector arranged so as to surround the plurality of metal lead frames together and formed of a light-reflecting resin.
  • the light-emitting element has electrodes of different polarities electrically connected respectively to different ones of the metal lead frames, and the light-emitting element is located inside the reflector and sealed in a light-transmitting resin.
  • the light-emitting element is arranged inside a recess formed by bending the metal lead frame.
  • the reflector has a resin reflective face located outside the recess in the metal lead frame and inclined relative to a bottom face of the recess.
  • the recess in the metal lead frame has, as metal reflective faces, a plurality of side faces inclined relative to the bottom face.
  • the resin reflective face has a resin inclined face inclined relative to the bottom face at an inclination angle ⁇ s 1 (°) smaller than the inclination angle ⁇ s 2 .
  • an illumination device is provided with a light-emitting device as described above for illuminating an illumination target.
  • a backlight for a display device is provided with: a light-emitting device as described above; and a light guide plate for guiding therethrough the light from the light-emitting device to illuminate a liquid crystal display panel.
  • the present invention it is possible, by arranging a light-emitting element inside a recess in a metal lead frame, to suppress discoloration of an inner wall of a reflector and prolong the lifetime of a device, and simultaneously, by fulfilling formulae (1) and (2), to satisfactorily improve the efficiency of light extraction to outside.
  • FIG. 1A is a plan view of an LED package as a light-emitting device according to one embodiment of the present invention
  • FIG. 1B is a sectional view of the LED package across a sectional plane perpendicular to the shorter-side thereof;
  • FIG. 1C is a sectional view of the LED package across a sectional plane perpendicular to the longer-side thereof;
  • FIG. 2 is a diagram illustrating an example of the shape of a reflector for reflecting light from an LED chip
  • FIG. 3 is a diagram illustrating another example of the shape of the reflector
  • FIG. 4 is a perspective view showing the exterior appearance of the reflector in FIG. 3 ;
  • FIG. 5 is a diagram illustrating yet another example of the shape of the reflector and schematically showing how light travels when the reflector is used;
  • FIG. 6 is a diagram illustrating the reflector in FIG. 5 on an enlarged scale
  • FIG. 7 is a diagram illustrating how light emergent from an LED chip at angles in a predetermined range travels
  • FIG. 8 is a diagram illustrating how light emergent at angles in a different range than mentioned above travels
  • FIG. 9 is a diagram illustrating how light emergent at angles in a still different range than mentioned above travels.
  • FIG. 10 is a diagram illustrating a light distribution pattern in light emission from the top face of a blue LED
  • FIG. 11 is a diagram illustrating a light distribution pattern in light emission by a phosphor
  • FIG. 12 is a diagram illustrating a light distribution pattern of a light source sealed in resin
  • FIG. 13 shows plots of the proportion of light that can exit from sealing resin directly into the atmosphere
  • FIG. 14 is a diagram illustrating how light emergent from an LED chip and incident on an interface between light-transmitting resin and a layer of air at angles in a predetermined range travels;
  • FIG. 15 is a diagram illustrating how light emergent from an LED chip and incident on the interface at angles in a different range than mentioned above travels;
  • FIG. 16 is a diagram illustrating how light travels when light incident on the interface at angles in the predetermined rage is totally reflected there and is extracted to outside via a reflector;
  • FIG. 17 is a diagram illustrating how light incident on the interface at angles in the predetermined range travels when the inclination angle of a resin reflective face of the reflector is equal to a critical angle;
  • FIG. 18 is a diagram illustrating how light incident on the interface at angles in the predetermined range travels when the inclination angle of a resin reflective face of the reflector is larger than a critical angle;
  • FIG. 19 is a diagram illustrating how light travels when light incident on the interface is totally reflected there, is then reflected on a reflective face of the reflector, and is then incident on the interface again;
  • FIG. 20 is a diagram illustrating how light travels when the inclination angle of a resin reflective face of the reflector is significantly smaller than a critical angle
  • FIG. 21 shows plots of the inclination angle fulfilling formula (1) against the index of refraction of light-transmitting resin
  • FIG. 22 is a diagram illustrating how light emerging sideways from an LED chip travels in the LED package
  • FIG. 23 is a diagram illustrating part of the LED package in FIG. 22 on an enlarged scale
  • FIG. 24 is a diagram illustrating how light emergent from a side face of an LED chip travels with an inclination relative to an axis perpendicular to the side face;
  • FIG. 25 is a diagram illustrating how light emergent from a side face of an LED chip is regularly reflected upward (toward an interface) on a metal reflective face;
  • FIG. 26 is a diagram illustrating how light emergent from a side face of an LED chip is regularly reflected downward on a metal reflective face
  • FIG. 27 is a diagram illustrating how light emergent from a side face of an LED chip with a downward inclination of 20° travels
  • FIG. 28 is a diagram illustrating how light emergent from a side face of an LED chip with an upward inclination of 20° travels
  • FIG. 29 is a simplified sectional view of the LED package
  • FIG. 30A is a plan view showing another structure of the LED package
  • FIG. 30B is a sectional view of the LED package across a sectional plane perpendicular to the shorter-side direction thereof;
  • FIG. 30C is a sectional view of the LED package across a sectional plane perpendicular to the longer-side direction thereof;
  • FIG. 31A is a plan view showing yet another structure of the LED package
  • FIG. 31B is a sectional view of the LED package across a sectional plane perpendicular to the shorter-side direction thereof;
  • FIG. 31C is a sectional view of the LED package across a sectional plane perpendicular to the longer-side direction thereof;
  • FIG. 32A is a plan view showing still another structure of the LED package
  • FIG. 32B is a sectional view of the LED package across a sectional plane perpendicular to the shorter-side direction thereof;
  • FIG. 32C is a sectional view of the LED package across a sectional plane perpendicular to the longer-side direction thereof;
  • FIG. 33A is a plan view showing still another structure of the LED package
  • FIG. 33B is a sectional view of the LED package across a sectional plane perpendicular to the shorter-side direction thereof;
  • FIG. 33C is a sectional view of the LED package across a sectional plane perpendicular to the longer-side direction thereof;
  • FIG. 34A is a plan view showing still another structure of the LED package
  • FIG. 34B is a sectional view of the LED package across a sectional plane perpendicular to the shorter-side direction thereof;
  • FIG. 34C is a sectional view of the LED package across a sectional plane perpendicular to the longer-side direction thereof;
  • FIG. 35A is a plan view showing still another structure of the LED package
  • FIG. 35B is a sectional view of the LED package across a sectional plane perpendicular to the shorter-side direction thereof;
  • FIG. 35C is a sectional view of the LED package across a sectional plane perpendicular to the longer-side direction thereof;
  • FIG. 36 is a sectional view showing still another structure of the LED package, and is a sectional view across a sectional plane perpendicular to the shorter-side direction thereof;
  • FIG. 37A is a plan view showing still another structure of the LED package.
  • FIG. 37B is a sectional view of the LED package
  • FIG. 37C is a sectional view of the LED package across a different sectional plane than FIG. 37B ;
  • FIG. 38A is a plan view showing still another structure of the LED package.
  • FIG. 38B is a sectional view of the LED package
  • FIG. 39 is an exploded perspective view showing an outline of the structure of an illumination device to which the LED package is applied.
  • FIG. 40 is a sectional view showing an outline of the structure of a liquid crystal display device provided with a backlight for a display device to which the LED package is applied.
  • FIG. 1A is a plan view of an LED package 1 as a light-emitting device according to one embodiment of the present invention
  • FIG. 1B is a sectional view of the LED package 1 across a sectional plane perpendicular to the shorter-side direction thereof
  • FIG. 1C is a sectional view of the LED package 1 across a sectional plane perpendicular to the longer-side direction thereof.
  • the region in FIG. 1A to clarify the region of a later-described metal lead frame 2 , the region is indicated, for convenience' sake, by the same hatching as in the sectional view (the same applies to other similar plan views).
  • the LED package 1 is rectangular as seen in a plan view, and is structured as follows: an LED chip 3 as a light-emitting element is arranged on a metal lead frame 2 ; the metal lead frame 2 is surrounded by a reflector 4 ; the LED chip 3 located inside (an opening 4 b of) the reflector 4 is sealed in with light-transmitting resin 5 .
  • the directions along the longer sides and along the shorter sides of the LED package 1 are also referred to simply as the longer-side direction (the left/right direction in FIG. 1A ) and the shorter-side direction (the up/down direction in FIG. 1A ) respectively.
  • the metal lead frame 2 comprises two metal lead frames 21 and 22 which are arranged apart from each other in the longer-side direction and which are electrically connected to an external power supply. These metal lead frames 21 and 22 are together surrounded by the reflector 4 .
  • the LED chip 3 is arranged on one metal lead frame 21 . In the embodiment, the LED chip 3 comprises two LED chips 31 and 32 which are arranged, side by side in the longer-side direction, inside a recess 21 p formed by bending the metal lead frame 21 .
  • the recess 21 p has, as a metal reflective face 21 a , a side face which is inclined relative to a bottom face 21 m on which the LED chip 3 is arranged inside the recess 21 p .
  • the metal reflective face 21 a comprises, on one hand, two metal reflective faces 21 a 1 and 21 a 2 that are located opposite each other across the bottom face 21 m and that are located along the longer-side direction and, on the other hand, two metal reflective faces 21 a 3 and 21 a 4 that are located opposite each other across the bottom face 21 m and that are located along the shorter-side direction.
  • the depth of the recess 21 p is greater than the thickness of the LED chips 31 and 32 .
  • the LED chips 31 and 32 each comprise a light-emitting diode that emits blue light.
  • the light-transmitting resin 5 in which the LED chip 3 is sealed, contains a yellow phosphor (phosphorescent or fluorescent substance) that absorbs blue light and emits yellow light.
  • the LED package 1 as a whole can, by mixing the blue and yellow light, emit white light.
  • Adding the yellow phosphor to the light-transmitting resin 5 makes it possible to use a high-luminance blue LED chip 3 as a light-emitting element, and thus to realize an LED package 1 that is suitable, as will be described later, as a backlight for a liquid crystal display device and as an illumination device for indoor illumination.
  • first electrode 31 a and 32 a can each be one of an anode electrode and a cathode electrode
  • the second electrodes 31 b and 32 b can each be the other of an anode electrode and a cathode electrode.
  • the first electrode 31 a of the LED chip 31 is connected to the metal lead frame 22 by a metal lead 6
  • the second electrode 31 b of the LED chip 31 is connected to the first electrode 32 a of the LED chip 32 by a metal lead 6
  • the second electrode 32 b of the LED chip 32 is connected to the metal lead frame 21 by a metal lead 6 .
  • the electrodes of different polarities of the LED chip 31 are electrically connected to different metal lead frames, each at least via a metal lead.
  • the electrodes of different polarities of the LED chip 32 are electrically connected to different metal lead frames, each at least via a metal lead.
  • the reflector 4 is formed of white or whitish resin that is light-reflecting resin, and has a resin reflective face 4 a which is located outside the recess 21 p in the metal lead frame 21 and which is inclined relative to a bottom face 21 m of the recess 21 p .
  • the resin reflective face 4 a has a resin inclined face that is inclined at an inclination angle ⁇ s 1 (°) smaller than the inclination angle ⁇ s 2 relative to the bottom face 21 m .
  • the resin reflective face 4 a comprises, on one hand, two resin inclined faces 4 a 1 and 4 a 2 that are located opposite each other across the recess 21 p and that are located in the longer-side direction and, on the other hand, two resin inclined faces 4 a 3 and 4 a 4 that are located opposite each other across the recess 21 p and that are located in the shorter-side direction.
  • the space surrounded by these four resin inclined faces 4 a 1 to 4 a 4 forms the opening 4 b in the reflector 4 , and this opening 4 b is filled with the light-transmitting resin 5 .
  • the critical angle ⁇ c sin ⁇ 1 ( n 0/ n ).
  • FIGS. 2 and 3 are diagrams illustrating the results of simulations done with respect to the shape of the reflector 4 .
  • the reflective face of the reflector 4 is parabolic in shape, and that the center of the top face of the LED chip 3 is located at the focus of the parabola.
  • the light that is emergent from the center of the top face of the LED chip 3 and is then incident on the intersection between the reflective face of the reflector 4 and the interface B between the light-transmitting resin 5 and the layer of air forms an angle ⁇ 0 (°) relative to the axis perpendicular to the top face of the LED chip 3 .
  • the light emergent from the top face of the LED chip 3 either is directly incident on the interface B and is extracted to outside (into the atmosphere), or is first reflected on the reflective face of the reflector 4 and is then extracted to outside through the interface B.
  • a deep reflector 4 such that ⁇ 0 ⁇ c as shown in FIG. 2
  • the light emergent from the top face of the LED chip 3 either is directly incident on the interface B and is extracted to outside (into the atmosphere), or is first reflected on the reflective face of the reflector 4 and is then extracted to outside through the interface B.
  • FIG. 4 is a perspective view schematically showing the exterior appearance of a reflector 4 having a steep inclined face as the resin reflective face 4 a .
  • This type of reflector 4 can be used in light-emitting devices of a side-view type for backlights in medium- and small-size liquid crystal panels.
  • FIG. 5 is a diagram schematically illustrating how light travels when a shallow reflector 4 is used to cope with a flat package
  • FIG. 6 is a diagram illustrating the reflector 4 shown in FIG. 5 on an enlarged scale.
  • the light emergent from the center of the top face of the LED chip 3 will be divided into three parts (a), (b), and (c) as noted below, which will be studied separately. It is assumed that the angle of the light emergent from the center of the top face of the LED chip 3 relative to the axis perpendicular to the top face of the LED chip 3 equals ⁇ t(°).
  • FIG. 7 is a diagram illustrating the path of the light emergent from the LED chip 3 in the range of angles (a). In this range of angles, light is totally reflected on the interface B between the light-transmitting resin 5 and the layer of air and is confined inside the package, and part of the light becomes stray light inside the package and is eventually absorbed.
  • FIG. 8 is a diagram illustrating the path of the light emergent from the LED chip 3 in the range of angles (b). In this range of angles, all the light emergent from the LED chip 3 is extracted into the layer of air without being totally reflected at the interface B.
  • FIG. 9 is a diagram illustrating the path of the light emergent from the LED chip 3 in the range of angles (c). In this range of angles, the light emergent from the LED chip 3 is first reflected on the reflector 4 and is then extracted to outside through the interface B.
  • FIG. 10 is a diagram illustrating a light distribution pattern in light emission from the top face of a junction-up blue LED that emits blue light.
  • the light distribution pattern of a blue LED is often approximated, as indicated by a thick solid line in FIG. 10 , a Lambertian light distribution pattern.
  • FIG. 11 is a diagram illustrating a light distribution pattern in light emission by a phosphor.
  • the light distribution pattern of a phosphor is, as indicated by a thick solid line in FIG. 11 , a pattern that is uniform in the circumferential direction.
  • the radiation intensity of the blue LED is represented by r ⁇ cos ⁇ a
  • the radiation intensity of the phosphor is represented by r.
  • FIG. 12 shows the light distribution patterns of light sources (an LED chip 3 and a phosphor 3 ′) flat-sealed in resin (with an index of refraction n) extending infinitely in two-dimensional directions.
  • the light distribution patterns of the LED chip 3 and the phosphor 3 ′ can be considered similar to those shown in FIGS. 10 and 11 respectively.
  • ⁇ c the critical angle of the light that travels out of the sealing resin into the atmosphere.
  • FIG. 13 show plots, for Lambertian and uniform radiation respectively, of the proportion of the light that directly exits from the sealing resin into the atmosphere against the index of refraction n of the sealing resin ranging from 1.4 to 1.6.
  • the proportion of light that directly exits into the atmosphere is, for Lambertian radiation, less than 45% and, for uniform radiation, less than 13%.
  • the proportion of the light that directly exits from the sealing resin into the atmosphere is, at best, less than 50% in ideal light emission by an LED chip and less than 15% in light emission by a phosphor.
  • FIG. 14 is a diagram illustrating the path of the light emergent from the LED chip 3 and incident on the interface B at angles in the range (d). In this range of angles, the light emergent from the LED chip 3 is totally reflected on the interface B and is confined inside the package.
  • FIG. 15 is a diagram illustrating the path of the light emergent from the LED chip 3 and incident on the interface B at angles in the range (e). In this range of angles, the light emergent from the LED chip 3 is extracted into the layer of air through the interface B.
  • the resin reflective face 4 a is inclined at an inclination angle ⁇ s 1 (relative to the bottom face 21 m of the recess 21 p ) such that rays incident on the interface B at the critical angle ⁇ c (also referred to as rays at the critical angle) are totally reflected on the interface B and are then incident on the resin reflective face 4 a of the reflector 4 perpendicularly thereto.
  • the light incident on the interface B at an angle of incidence ⁇ is first totally reflected on the interface B, is then regularly reflected on the resin reflective face 4 a of the reflector 4 , and is then incident on the interface B again.
  • the angle of incidence with respect to the interface B is smaller, namely 2 ⁇ c ⁇ .
  • the angle of incidence (2 ⁇ c ⁇ ) of the light that is incident on the interface B again is always equal to or smaller than ⁇ c, permitting this light to exit through the interface B.
  • FIG. 18 is a diagram illustrating how, when ⁇ s 1 > ⁇ c, the light in the range of angles (d) above travels.
  • FIG. 19 shows how the light incident at a point of incidence 1 on the interface B is totally reflected there, is then reflected at a point of reflection on the resin reflective face 4 a of the reflector 4 , and is then incident at a point of incidence 2 on the interface B again.
  • the conditions for the light incident on the interface B at angles ⁇ and ⁇ ′ is totally reflected there are, respectively, ⁇ c and ⁇ ′ ⁇ c , i.e., ⁇ +2( ⁇ s 1 ⁇ ) ⁇ c. These can be merged to obtain ⁇ c ⁇ 2 ⁇ s 1 ⁇ c. This expression can be further modified to obtain ⁇ c ⁇ c+ 2( ⁇ s 1 ⁇ c ). That is, the light that is incident on the interface B for the first time in this range of angles is regularly reflected on the resin reflective face 4 a of the reflector 4 , and is then, when incident on the interface B again, totally reflected on the interface B; thus, the light cannot be extracted to outside.
  • the light that is incident on the interface B in the range ⁇ > ⁇ c+ 2( ⁇ s 1 ⁇ c ) is, after reflection on the reflector, so incident on the interface B again as to be extracted out of the package. (About ⁇ s 1>45° ⁇ c/ 2)
  • FIG. 20 is a diagram illustrating how light travels when the inclination angle ⁇ s 1 of the resin reflective face 4 a of the reflector 4 is significantly smaller than the critical angle.
  • the critical angle ⁇ s 1 in formula (1) taking a value close to the upper limit, i.e., the critical angle ⁇ c, or a value close to the lower limit, namely 45° ⁇ c/2.
  • the inclination angle ⁇ s 1 is close to 22.5°+ ⁇ c/4, which is the mid value between the upper and lower limits of formula (1).
  • FIG. 21 shows plots of the inclination angle ⁇ s 1 that fulfills formula (1) against the index of refraction n of the light-transmitting resin 5 .
  • the recess 21 p is formed in the metal lead frame 2 , and the LED chip 3 is arranged inside the recess 21 p .
  • This structure (a) gives an increased distance from the LED chip 3 to the resin reflective face 4 a of the reflector 4 , and (b) helps reduce the amount of light that is incident from the LED chip 3 directly on the reflector 4 .
  • the LED package 1 according to the embodiment employing a blue LED with extremely high luminance is suitable in backlights for display devices such as liquid crystal panel televisions and in illumination devices for illuminating illumination targets.
  • the light emergent sideways from the LED chip 3 can mostly be reflected on the metal reflective face 21 a of the recess 21 p so as not to be incident directly on the reflector 4 across a short distance, and this helps reliably suppress deterioration of the inner wall of the reflector 4 .
  • FIG. 22 is a diagram illustrating how the light emergent sideways from the LED chip 3 travels in the LED package 1 according to the embodiment.
  • the LED chip 3 is surrounded by the side face (metal reflective face 21 a ) of the recess 21 p in the metal lead frame 2 , and thus much of the light radiated sideways from the chip is reflected on the metal reflective face 21 a so as to be deflected frontward.
  • the metal reflective face 21 a of the recess 21 p an appropriate inclination angle, it is possible to extract light efficiently out of the light-transmitting resin 5 .
  • FIG. 23 is a diagram illustrating, on an enlarged scale, part of the LED package 1 shown in FIG. 22 .
  • the metal reflective face 21 a an inclination angle ⁇ s 2 such that, when light is reflected on the metal lead frame 2 , as much light as possible enters a conical region with an apical angle 2 ⁇ c having its apex at the point of reflection.
  • the light that has entered the conical region is incident on the interface B at angles smaller than the critical angle ⁇ c, and thus it can be extracted without being totally reflected on the interface B back inside the package.
  • the inclination angle ⁇ s 2 of the metal reflective face 21 a equal 45°.
  • the light emergent in the direction (axial direction) perpendicular to the chip side face is, when reflected on the metal reflective face 21 a with an inclination angle of 45°, deflected through 90°, and is thus incident on the interface B perpendicularly thereto.
  • the light emergent from the chip side face at angles close to perpendicular thereto is incident on the interface B with slight inclinations relative to the direction perpendicular thereto.
  • light can be efficiently extracted out of the package with almost no reflection on the interface B.
  • ⁇ s 2 45.
  • the direction in which the light emergent from the chip side face has the maximum intensity can be inclined from the axis perpendicular to the chip side face.
  • FIG. 24 is a diagram illustrating how light emergent from the chip side face travels with an inclination relative to the axis perpendicular to the chip side face.
  • the light emergent from the side face of the LED chip 3 in a direction inclined at an angle of ⁇ 0 (°) relative to the axis perpendicular to the side face forms an angle ⁇ (°) relative to the axis perpendicular to the interface B.
  • the just-mentioned light is, when regularly reflected on the metal reflective face 21 a , deflected through ⁇ (°), and that the light after regular reflection forms an angle ⁇ ′ (°) relative to the axis perpendicular to the interface B.
  • the inclination angle ⁇ s 2 of the metal reflective face 21 a such that the angle ⁇ ′ equals 0 even when light emergent from the chip side face travels in a direction inclined relative to the axis perpendicular to the chip side face, it is possible to make the light regularly reflected on the metal reflective face 21 a incident on the interface B perpendicularly thereto, and to extract the light efficiently.
  • the inclination angle ⁇ s 2 of the metal reflective face 21 a can vary within the range of 45° ⁇ 10°. Accordingly, with such a light distribution pattern taken into account, fulfilling formula (2) noted above makes it possible to make the light emergent sideways from the chip incident on the interface B approximately perpendicularly thereto via the metal reflective face 21 a . It can safely be said that, in this way, light can be extracted efficiently without reflection on the interface B.
  • the inclination angle ⁇ s 2 of the metal reflective face 21 a it is particularly preferable to set the inclination angle ⁇ s 2 of the metal reflective face 21 a at 45°.
  • FIG. 29 is a simplified sectional view of the LED package 1 described above. It is preferable that the LED package 1 further fulfill formula (3) below: D> 2 ⁇ d ⁇ tan ⁇ c (3) where
  • the light radiated inside the cone with an apex angle 2 ⁇ c can be extracted to outside without total reflection on the interface B between the light-transmitting resin 5 and the layer of air, but the light radiated outside the cone is incident on the interface B at angles of incidence equal to or larger than the critical angle and is thus totally reflected there.
  • the structure according to the embodiment which improves the efficiency of extraction of such totally reflected light, is extremely effective in a flat LED package 1 as described above (where d is far smaller than D).
  • Fulfilling formula (1) noted above for at least one of the four resin inclined faces 4 a 1 to 4 a 4 (see FIG. 1 ) constituting the resin reflective face 4 a gives an effect of improving light extraction efficiency; fulfilling it for all the resin inclined faces 4 a 1 to 4 a 4 gives the maximal effect, and is therefore preferable.
  • Fulfilling formula (2) noted above for at least one of the four metal reflective faces 21 a 1 to 21 a 4 (see FIG. 1 ) constituting the metal reflective face 21 a allows efficient extraction of the light emergent sideways from the chip through the interface B via the metal reflective face 21 a ; fulfilling it for all the metal reflective faces 21 a 1 to 21 a 4 gives the maximal effect, and is therefore preferable.
  • each of the resin inclined faces 4 a 1 to 4 a 4 fulfill ⁇ s 1 ⁇ s 2 for each of the metal reflective faces 21 a 1 to 21 a 4 , that formula (1) is fulfilled for each of the resin inclined faces 4 a 1 to 4 a 4 , and that formula (2) is fulfilled for each of the metal reflective faces 21 a 1 to 21 a 4 .
  • the LED package 1 shown in FIG. 1 is designed to fulfill those conditions.
  • the two metal reflective faces 21 a 3 to 21 a 4 Among the four metal reflective faces 21 a 3 to 21 a 4 , the two metal reflective faces 21 a 3 and 21 a 4 located along the shorter-side direction have a smaller area than the two metal reflective faces 21 a 1 and 21 a 2 located along the longer-side direction, thus receive less light from the LED chip 3 , and thus have a smaller effect on light extraction efficiency.
  • formula (1) is fulfilled for each of the four resin inclined faces 4 a 1 to 4 a 4 and in addition formula (2) is fulfilled for the two metal reflective faces 21 a 1 and 21 a 2 located along the longer-side direction, it is possible to improve the efficiency of light extraction to outside.
  • FIG. 30A is a plan view showing another structure of the LED package 1
  • FIG. 30B is a sectional view of the LED package 1 across a sectional plane perpendicular to the shorter-side direction thereof
  • FIG. 30C is a sectional view of the LED package 1 across a sectional plane perpendicular to the longer-side direction thereof.
  • This LED package 1 is so designed that, among the four resin inclined faces 4 a 1 to 4 a 4 , the two resin inclined faces 4 a 3 and 4 a 4 located along the shorter-side direction each fulfill ⁇ s 1 ⁇ s 2 for, among the fourth metal reflective faces 21 a 1 to 21 a 4 , the two metal reflective faces 21 a 1 and 21 a 2 locate along the longer-side direction.
  • formula (1) is fulfilled for the two resin inclined faces 4 a 3 and 4 a 4 located along the shorter-side direction
  • formula (2) is fulfilled for the two metal reflective faces 21 a 1 and 21 a 2 located along the longer-side direction.
  • FIG. 31A is a plan view showing yet another structure of the LED package 1
  • FIG. 31B is a sectional view of the LED package 1 across a sectional plane perpendicular to the shorter-side direction thereof
  • FIG. 31C is a sectional view of the LED package 1 across a sectional plane perpendicular to the longer-side direction thereof.
  • This LED package 1 has a similar design as the one shown in FIG. 30 except that the dimension in the shorter-side direction is smaller than in FIG. 30 .
  • the LED package 1 of the embodiment is applied to a backlight 210 in a later-described liquid crystal display device 200 (see FIG. 40 ).
  • slimming down the backlight 210 necessitates reducing the dimension of the LED package 1 in the shorter-side direction, which corresponds to the thickness direction of a light guide plate 213 .
  • the direction in which the inclination angle of the resin inclined faces 4 a 3 and 4 a 4 is reduced corresponds to the direction in which the dimension of the LED package 1 in the longer-side direction is increased, but this direction is unrelated to the slimming down of the backlight 210 , and is therefore subject to no restriction whatever.
  • the resin inclined faces 4 a 3 and 4 a 4 allow more freedom than the resin inclined faces 4 a 1 and 4 a 2 , making it easier for the former than for the latter to work out a design fulfilling formula (1). Accordingly, by fulfilling formula (1) for the two resin inclined faces 4 a 3 and 4 a 4 located along the shorter-side direction, it is possible to improve light extraction efficiency with a structure compatible with the flat backlight 210 .
  • the two metal reflective faces 21 a 1 to 21 a 4 have a larger area than the two metal reflective faces 21 a 3 and 21 a 4 located along the shorter-side direction, and thus receive more light from the LED chip 3 . Accordingly, by fulfilling formula (2) for the two metal reflective faces 21 a 1 and 21 az located along the longer-side direction, it is possible to more efficiently extract the light that is emergent sideways from the LED chip 3 and is incident on the interface B via the metal reflective face 21 a.
  • FIG. 32A is a plan view showing still another structure of the LED package 1
  • FIG. 32B is a sectional view of the LED package 1 across a sectional plane perpendicular to the shorter-side direction thereof
  • FIG. 32C is a sectional view of the LED package 1 across a sectional plane perpendicular to the longer-side direction thereof.
  • This LED package 1 is so designed that, among the four resin inclined faces 4 a 1 to 4 a 4 , the two resin inclined faces 4 a 1 and 4 a 2 located along the longer-side direction each fulfill ⁇ s 1 ⁇ s 2 for, among the four metal reflective faces 21 a 1 to 21 a 4 , the two metal reflective faces 21 a 1 and 21 a 2 located along the longer-side direction.
  • formula (1) is fulfilled for the two resin inclined faces 4 a 1 and 4 a 2 located along the longer-side direction
  • formula (2) is fulfilled for the two metal reflective faces 21 a 1 and 21 a 2 located in the longer-side direction.
  • FIG. 33A is a plan view showing yet another structure of the LED package 1
  • FIG. 33B is a sectional view of the LED package 1 across a sectional plane perpendicular to the shorter-side direction thereof
  • FIG. 33C is a sectional view of the LED package 1 across a sectional plane perpendicular to the longer-side direction thereof.
  • This LED package 1 has a similar design as the one shown in FIG. 32 except that a single LED chip 3 is used and that the dimension of the package in the longer-side direction is shorter.
  • the two resin inclined faces 4 a 1 and 4 a 2 located along the longer-side direction of the LED package 1 have a larger area than the two resin inclined faces 4 a 3 and 4 a 4 located along the shorter-side direction, and thus receive more light.
  • formula (1) for the two resin inclined faces 4 a 1 and 4 a 2 located along the longer-side direction it is possible to extract the light incident on the interface B.
  • the LED package 1 is applied to a later-described illumination device 100 (see FIG. 39 )
  • the dimension of the LED package 1 in the shorter-side direction is subject to no restriction.
  • the LED package 1 designed as shown in FIGS. 32 and 33 is suitable for an illumination device 100 .
  • the two metal reflective faces 21 a 1 and 21 a 2 located along the longer-side direction of the LED package 1 have a larger area than the two metal reflective faces 21 a 3 and 21 a 4 located along the shorter-side direction, and receive more light from the LED chip 3 .
  • formula (2) for the two metal reflective faces 21 a 1 and 21 a 2 it is possible to efficiently extract the light that is emergent sideways from the LED chip 3 and is incident on the interface B via the metal reflective face 21 a.
  • the structure according to the embodiment which helps improve light extraction efficiency, is extremely effective in cases where a plurality of LED chips are arranged side by side in the longer-side direction.
  • FIG. 34A is a plan view showing yet another structure of the LED package 1
  • FIG. 34B is a sectional view of the LED package 1 across a sectional plane perpendicular to the shorter-side direction thereof
  • FIG. 34C is a sectional view of the LED package 1 across a sectional plane perpendicular to the longer-side direction thereof.
  • the metal lead frame 2 can comprise three metal lead frames 21 to 23 which are electrically connected to an external power supply.
  • the LED chips 31 and 32 can be arranged on separate metal lead frames 21 and 23 .
  • the first electrode 31 a of the LED chip 31 can be connected to the metal lead frame 21 by a metal lead 6
  • the second electrode 31 b of the LED chip 31 can be connected to the metal lead frame 22 by a metal lead 6
  • the first electrode 32 a of the LED chip 32 can be connected to the metal lead frame 22 by a metal lead 6
  • the second electrode 32 b of the LED chip 32 can be connected to the metal lead frame 23 by a metal lead 6 .
  • FIG. 35A is a plan view showing yet another structure of the LED package 1
  • FIG. 35B is a sectional view of the LED package 1 across a sectional plane perpendicular to the shorter-side direction thereof
  • FIG. 35C is a sectional view of the LED package 1 across a sectional plane perpendicular to the longer-side direction thereof.
  • the LED package 1 can be provided with a single LED chip 3 as in FIG. 33 .
  • the first electrode 31 a of the LED chip 31 can be connected to the metal lead frame 22 by a metal lead 6
  • the second electrode 31 b of the LED chip 31 can be connected to the metal lead frame 21 , on which the LED chip 31 is arranged, by a metal lead 6 .
  • FIG. 36 is a sectional view showing still another structure of the LED package 1 , and is a sectional view across a sectional plane perpendicular to the shorter-side direction of the LED package 1 .
  • the resin reflective face 4 a of the reflector 4 can include, as part of it, a steep inclined face 41 . That is, the resin reflective face 4 a can comprise a resin inclined face 42 with an inclination angle ⁇ s 1 and a steep inclined face 41 with an inclination angle larger than that of the inclined face 42 . Any number of steep inclined faces 41 can be provided; that is, the number of steep inclined faces 41 can be one, or two as in FIG. 36 , or more.
  • formula (1) has only to be fulfilled for at least part of the resin reflective face 4 a.
  • FIG. 37A is a plan view showing still another structure of the LED package 1
  • FIGS. 37B and 37C are sectional views of the LED package 1 across different sectional planes thereof.
  • the LED package 1 can be formed to be square in shape as seen in a plan view.
  • the shape of the metal lead frames 21 and 22 can be determined according to the shape of the LED package 1 as seen in a plan view. That is, the shape of the metal lead frames 21 and 22 can be determined such that, when arranged apart from each other, they together define a square as seen in a plan view.
  • FIG. 38A is a plan view showing still another structure of the LED package 1
  • FIG. 38B is a sectional view of the LED package 1
  • the LED package 1 can be formed to be circular in shape as seen in a plan view.
  • the shape of the metal lead frames 21 and 22 can be determined according to the shape of the LED package 1 as seen in a plan view. That is, the shape of the metal lead frames 21 and 22 can be determined such that, when arranged apart from each other, they together define a circle as seen in a plan view.
  • the resin reflective face 4 a comprises a resin inclined face that extends continuously in the direction along the circumference of the package.
  • the effect of improving light extraction efficiency in the package described above depends greatly on various factors such as the size of the actual package, the reflection properties of the actually used reflector resin and metal frame, the index of refraction of the sealing resin, whether a phosphor is contained or not, and the size and characteristics of the chip. In general, an improvement of about 4% to 12% is expected. In cases where the actually used reflector resin and metal frame have especially low reflectance, a higher improvement, for example over the just-mentioned 12%, may be achieved.
  • FIG. 39 is an exploded perspective view showing an outline of the structure of an illumination device 100 as an application example of the LED package 1 according to the embodiment.
  • the illumination device 100 is, for example, installed indoors or outdoors for illumination of an illumination target (for example, a space or a person), and includes a light source 101 which projects light and a housing 102 in which the light source 101 is housed.
  • the illumination device 100 can also include a heat radiator for rejecting the heat of the light source 101 .
  • the light source 101 is composed of a plurality of LED packages 101 a arranged in a ring form on a base 102 b , and is fixed to the housing 102 by an unillustrated holder.
  • Each of the LED packages 101 a comprises the LED package 1 of the embodiment described previously.
  • the housing 102 has a socket coupler 102 a which is coupled to an electricity socket (unillustrated) and a body 102 which is contiguous with the socket coupler 102 a and which houses the light source 101 .
  • FIG. 40 is sectional view showing an outline of the structure of a liquid crystal display device 200 provided with a backlight 210 for display devices as another application example of the LED package 1 of the embodiment.
  • the liquid crystal display device 200 has a backlight 210 and a liquid crystal panel 220 .
  • the backlight 210 has an LED package 211 , a mounting circuit board 212 , and a light guide plate 213 .
  • the LED package 211 comprises the LED package 1 of the embodiment described previously, and is so mounted on the mounting circuit board 212 as to permit light to strike an end face of the light guide plate 213 which is arranged parallel to the mounting circuit board 212 .
  • the mounting circuit board 212 is supported on a device casing 231 .
  • the light from the LED package 211 enters the light guide plate 213 through the end face thereof and is guided therethrough so that the light eventually exits from the light guide plate 213 through a top face thereof so as to illuminate the liquid crystal panel 220 through an optical sheet 232 .
  • the liquid crystal panel 220 can, by modulating the light emergent from the light guide plate 213 according to image data, display an image.
  • the liquid crystal panel 220 is fixed to the device casing 231 by a frame 233 which is arranged to face the LED package 211 across a reflective sheet 234 .
  • the LED package 1 even in cases where a high-luminance blue LED is used, it is possible to suppress deterioration of white resin, to reduce a lowering in light output, and to prolong the lifetime of the package, and it is also possible to improve the efficiency of light extraction to outside. Accordingly, by applying this LED package 1 to an illumination device 100 or to a backlight 210 in a liquid crystal display device 200 , it is possible to realize an illumination device 100 and a backlight 210 that offer high luminance combined with a long lifetime.
  • an LED package 1 by appropriately combining together features from different structures described with reference to the respective drawings above, and to apply it to a backlight or an illumination device.
  • a light-emitting device, an illumination device, and a backlight for a display device according to the embodiment can be expressed as follows.
  • a light-emitting device is provided with: a light-emitting element arranged on one of a plurality of metal lead frames arranged apart from one another; and a reflector arranged so as to surround the plurality of metal lead frames together and formed of a light-reflecting resin.
  • the light-emitting element has electrodes of different polarities electrically connected respectively to different ones of the metal lead frames, and the light-emitting element is located inside the reflector and sealed in a light-transmitting resin.
  • the light-emitting element is arranged inside a recess formed by bending the metal lead frame.
  • the reflector has a resin reflective face located outside the recess in the metal lead frame and inclined relative to a bottom face of the recess.
  • the recess in the metal lead frame has, as metal reflective faces, a plurality of side faces inclined relative to the bottom face.
  • the resin reflective face has a resin inclined face inclined relative to the bottom face at an inclination angle ⁇ s 1 (°) smaller than the inclination angle ⁇ s 2 .
  • the critical angle of light emergent from the light-emitting element and incident on the interface between the light-transmitting resin and the layer of air equals ⁇ c (°)
  • formulae (1) and (2) below are simultaneously fulfilled: 45° ⁇ c/ 2 ⁇ s 1 ⁇ c, (1) 35° ⁇ s 2 ⁇ 55°.
  • the resin reflective face can comprise four resin reflective faces arranged respectively along the four sides of the quadrangle.
  • the resin reflective face can comprise a continuous reflective face arranged along the circumference of the circle.
  • the light-emitting element being arranged inside the recess formed by bending the metal lead frame, the light emergent sideways from the light-emitting element can be reflected on the side faces (metal reflective faces) of the recess to exit frontward.
  • the reflector light-reflecting resin
  • the inclination angle ⁇ s 1 of the resin inclined face then equals the mid value between the upper and lower limits of formula (1), and thus it is possible to improve light extraction efficiency with an amply margined design where the inclination angle ⁇ s 1 is away from both the upper and lower limits
  • the light emergent from the center of the top face of the light-emitting element includes light that is incident on the interface between the light-transmitting resin and the layer of air at angles of incidence equal to or larger than the critical angle and is totally reflected there.
  • the above-described structure according to the present invention which improves the efficiency of light extraction from the interface to outside, is extremely effective.
  • the depth of the recess in the metal lead frame can be equal to or greater than the thickness of the light-emitting element. It is then possible to reflect most of the light emergent sideways from the light-emitting element on the side faces of the recess so that it is not directly incident on the reflector. It is thus possible to reliably suppress deterioration of the inner wall of the reflector.
  • the light-emitting device is rectangular in shape as seen in a plan view;
  • the resin inclined face comprises resin inclined faces provided opposite each other across the recess along the longer-side direction of the light-emitting device and resin inclined faces provided opposite each other across the recess along the shorter-side direction of the light-emitting device;
  • the metal reflective faces comprise metal reflective faces provided opposite each other across the bottom face along the longer-side direction and metal reflective faces provided opposite each other across the bottom face along the shorter-side direction;
  • each of the four resin inclined faces fulfills ⁇ s 1 ⁇ s 2 with respect to each of the four metal reflective faces; formula (1) is fulfilled for each of the four resin inclined faces; and formula (2) is fulfilled for each of the four metal reflective faces.
  • the light-emitting device is rectangular in shape as seen in a plan view, by fulfilling formula (1) for each of the four resin inclined faces of the reflector and fulfilling formula (2) for each of the four metal reflective faces of the metal lead frame, it is possible to maximize the effect of improving light extraction efficiency in the light-emitting device.
  • the light-emitting device is rectangular in shape as seen in a plan view;
  • the resin inclined face comprises resin inclined faces provided opposite each other across the recess along the longer-side direction of the light-emitting device and resin inclined faces provided opposite each other across the recess along the shorter-side direction of the light-emitting device;
  • the metal reflective faces comprise metal reflective faces provided opposite each other across the bottom face along the longer-side direction and metal reflective faces provided opposite each other across the bottom face along the shorter-side direction;
  • each of the four resin inclined faces fulfills ⁇ s 1 ⁇ s 2 with respect to two of the four metal reflective faces located along the longer-side direction; formula (1) is fulfilled for each of the four resin inclined faces; and formula (2) is fulfilled for the two metal reflective faces located along the longer-side direction.
  • the two metal reflective faces located along the longer-side direction of the light-emitting device have a larger area than the two metal reflective faces located along the shorter-side direction, and receive more light from the LED.
  • formula (2) for the two metal reflective faces located along the longer-side direction, it is possible to efficiently extract the light that is emergent sideways from the light-emitting element and is incident on the interface via the metal reflective faces.
  • the light-emitting device is rectangular in shape as seen in a plan view;
  • the resin inclined face comprises resin inclined faces provided opposite each other across the recess along the longer-side direction of the light-emitting device and resin inclined faces provided opposite each other across the recess along the shorter-side direction of the light-emitting device;
  • the metal reflective faces comprise metal reflective faces provided opposite each other across the bottom face along the longer-side direction and metal reflective faces provided opposite each other across the bottom face along the shorter-side direction; each of two of the four resin inclined faces located along the shorter-side direction fulfills ⁇ s 1 ⁇ s 2 with respect to two of the four metal reflective faces located along the longer-side direction; formula (1) is fulfilled for the two resin inclined faces located along the shorter-side direction; and formula (2) is fulfilled for the two metal reflective faces located along the longer-side direction.
  • the two metal reflective faces located along the longer-side direction of the light-emitting device have a larger area than the two metal reflective faces located along the shorter-side direction, and receive more light from the LED.
  • formula (2) for the two metal reflective faces located along the longer-side direction, it is possible to efficiently extract the light that is emergent sideways from the light-emitting element and is incident on the interface via the metal reflective faces.
  • the light-emitting device according to the present invention is applied to a flat edge-lit backlight employing a light guide plate, it is necessary to reduce the dimension of the light-emitting device in the shorter-side direction, which corresponds to the thickness direction of the light guide plate.
  • the light-emitting device is rectangular in shape as seen in a plan view;
  • the resin inclined face comprises resin inclined faces provided opposite each other across the recess along the longer-side direction of the light-emitting device and resin inclined faces provided opposite each other across the recess along the shorter-side direction of the light-emitting device;
  • the metal reflective faces comprise metal reflective faces provided opposite each other across the bottom face along the longer-side direction and metal reflective faces provided opposite each other across the bottom face along the shorter-side direction; each of two of the four resin inclined faces located along the longer-side direction fulfills ⁇ s 1 ⁇ s 2 with respect to two of the four metal reflective faces located along the longer-side direction; formula (1) is fulfilled for the two resin inclined faces located along the longer-side direction; and formula (2) is fulfilled for the two metal reflective faces located along the longer-side direction.
  • the two resin inclined faces located along the longer-side direction of the light-emitting device have a larger area than the two resin inclined faces located along the shorter-side direction, and thus receive more of the light that is emergent from the light-emitting element and is totally reflected on the interface.
  • formula (1) for the two resin inclined faces located along the longer-side direction, it is possible to efficiently extract the light that is incident on the interface again.
  • the two metal reflective faces located along the longer-side direction of the light-emitting device have a larger area than the two metal reflective faces located along the shorter-side direction, and thus receives more of the light that is emergent sideways from the LED.
  • the light-emitting element can comprise a plurality of light-emitting elements arranged inside the recess side by side in the longer-side direction of the light-emitting device.
  • Arranging a plurality of light-emitting elements in such a way tends to increase, in the longer-side direction of the light-emitting device, the light that is incident on the interface at angles of incidence larger than the critical angle, leading to lower efficiency of light extraction from the interface.
  • the present invention which improves light extraction efficiency, is extremely effective in such a structure where a plurality of light-emitting elements are arranged side by side in the longer-side direction.
  • the light-transmitting resin can contain a phosphor.
  • a phosphor a substance that absorbs blue light and emits yellow light
  • an illumination device can incorporate a light-emitting device as described above for illuminating an illumination target. It is thus possible to realize an illumination device that offers high luminance combined with a long lifetime.
  • a backlight for a display device can incorporate a light-emitting device as described above and a light guide plate for guiding therethrough the light from the light-emitting device to illuminate a liquid crystal display panel. It is thus possible to realize a backlight for a display device that offers high luminance combined with a long lifetime.
  • Light-emitting devices find applications, for example, in illumination devices and in backlights for display devices.

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US14/410,469 2012-06-29 2013-05-15 Light-emitting device, illumination device and backlight for display device Active US9680076B2 (en)

Applications Claiming Priority (3)

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JP2012147826A JP5721668B2 (ja) 2012-06-29 2012-06-29 発光装置、照明装置および表示装置用バックライト
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WO2014002628A1 (ja) 2014-01-03
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